When arriving or leaving a destination it is a greeting that is generally AWESOME...but very stupid. If you say errday you are likely to be made fun of (because you are a retard).

It is commonly used by the the mentally unstable/ extremely high/ people who have been awake for an entire month.

The Err portion of the word can be strung out as long as the user desires...example ERrrrrrrrrrrrrrDay. But it is forbidden for the day portion to be stretched at all. By penatly of death in greater portions of Columbia.